Traditionally, in conventional processes for forming metal castings, a mold, such as a metal die or sand mold having an interior chamber with the exterior features of a desired casting defined therein, is filled with a molten metal. A sand core that defines interior features of the casting is received and or positioned within the mold to form the interior detail of the casting as the molten metal solidifies about the core. After the molten metal of the casting has solidified, the casting generally is moved to a treatment furnace(s) for heat treatment of the castings, removal of sand from the sand cores and/or molds, and other processing as required. The heat treatment processes condition the metal or metal alloys of the castings to achieve the desired physical characteristics for a given application.
Typically, during the transfer of the castings from the pouring station to a heat treatment station, and especially if the castings are allowed to sit for any appreciable amount of time, the castings may be exposed to the ambient environment of the foundry or metal processing facility. As a result, the castings tend to rapidly cool down from a molten or semi-molten temperature. While some cooling of the castings is necessary to allow the castings to solidify, the more the temperature of the castings drops, and the longer the castings remain below a process critical temperature (also referred to herein as the “process control temperature”) of the castings, the more time is required to heat the castings up to a desired heat treatment temperature and to heat treat the castings. For example, it has been found that for certain types of metals, for every minute of time that the casting drops below its process control temperature, at least about 4 minutes of extra heat treatment time is required to achieve the desired results. Thus, even dropping below the process control temperature for the metal of the casting for as few as ten minutes may require at least about 40 minutes of additional heat treatment time to achieve the desired physical properties. Typically, therefore, the castings are heat treated for 2 to 6 hours, in some cases longer, to achieve the desired heat treatment effects. This results in greater utilization of energy and, therefore, greater heat treatment costs.